1. Field of the Invention
This invention is directed to removal of ammonia compounds from materials and, in one aspect, to removal of ammonia from sludge.
2. Description of Related Art
In the treatment of wastewater, sludges are generated by the clarification of incoming wastewater to remove solids that are either inert or are too large to be easily biodegraded. Such solids can cause mechanical problems with downstream equipment. Primary sludges are generally gritty and odorous.
Denatured, primary, digested or secondary sludge consists of excess microbial mass generated as a result of a biological treatment process. During certain sludge digestion processes, a portion of the microbes decomposes to organic compounds, phosphorous and nitrogen in the form of ammonia. Such sludges and dewatered solids may have undesirably high levels of ammonia.
A variety of previous patents describe various apparatuses and processes. U.S. Pat. No. 4,984,162 describes a method of collecting vented material from vessels containing raw wastewater and volatile compounds that would normally escape to the atmosphere since these vessels normally have an open top. The vented material and air are pumped to an aerobic sludge reactor where the volatile and odorous compounds are destroyed by bacteria in the reactor and remaining biologically inert gas then degasses to the atmosphere.
U.S. Pat. No. 4,966,706 describes adding peracid to a sludge generated in a wastewater treatment plant to kill parthenogenic microorganisms and worm eggs. The peracid treated sludge is then digested in an anaerobic septic tank which generates methane that is burned to produce usable energy. The digested sludge can be used as fertilizer.
British patent application U.K. 2,202,167 describes a process for removing dissolved gasses from a liquid, particularly oxygen from water, using a static mixer and mentions removing volatile compounds from wastewater. The patent describes a separation tank where the gasses separate from the liquid without agitation.
Japanese Patent 53-144463 describes a process for removing gas from water using two ejectors and degassing tanks in series. This is similar to the previous patent except an ejector is used instead of a static mixer. Both devices are similar in that they mix a stripping gas with the liquid.
U.S. Pat. No. 4,160,725 describes a nonbiological steam stripper for removing ammonium and phenolic compounds from coke oven wastewater.
U.S. Pat. No. 4,508,545 describes a system using stripping gasses from wastewater in a packed tower and a gas scrubber so the stripping gas can be recycled.
U.S. Pat. No. 4,655,935 describes a process for detoxifying wastewater from dithiocarbamate manufacturing that includes air stripping the water.
British Patent U.K. 2,093,727 describes a method for enhanced thickening of anaerobically digested sludge. The sludge after digestion contains entrained methane. By stripping the sludge with a gas and degassing, the sludge thickens in a gravity settler.
There has long been a need for an effective and efficient method for the reduction of sludge ammonia content.